The Gb5 (GNB5 guanine nucleotide binding protein (G protein), beta 5) is a G protein subunit present predominantly in the central nervous system. This protein appears to be expressed in two forms, one found in the brain of 39kD and one found in the retina of 44kD. It has also been found that Gb5 associates tightly with RGS7, a member of the superfamily of negative regulators of G protein signaling. These complexes have been localized to most regions of the brain, whereas Gb1-4 exhibit no observable colocalization with RGS7, despite their widespread codistribution throughout similar neuronal networks. This antibody is specific for a peptide sequence within the D1 blade which is not found in Gb1-4.